Simultaneous bleaching and fixing bath



Patented June 15, 1943 2,322,084 SIMULTANEOUS BLmcniNG AND FIXING.

BATH

Richard V. Young and Merrill -W. Seymour, Rochester, N. Y.,- assignors toEastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application November 0,1940, Serial 1 In Great Britain January 11,

8 Claims. (01. 95-6) This invention relates to improvements in color photography and mor particularly in processes wherein dyes present in a silver halide emulsion are bleached in the vicinity of a ilver'image.

It is known that the bleaching of dyes selectively in the neighborhood of a silver image can be accomplished by reagents such as acid thiourea. It is possible'to control the contrast of the dye images by the addition of azo dyes or other mild oxidizing agents to the bleaching solutions which cause less image-forming dye to be reduced by a given amount of silver for the available reducing agent because they compete with the azo dyes present in the emulsion, as described in our application Serial No. 355,098 filed August 31, 1940. This lowers the contrast of the dye im- 8.868.

in the processes of thebleaching-out has hitherto been customary to fix out the un developed silver salts before treatment with the bleach baths. In such bleaching-out processes, moreover, there is generally some excess of silver left behind after the bleaching of the dye has been carried to the desired point. This residual silver has to be removed after oxidation with some reagent which does not destroy the yp it centrations of the oxidizing agent and of the other constituents. of the bleach bath may be altered as requiredto bleach the desired amount of dye in thetime necessary to oxidize all of the silver to a soluble silver complex.

The invention includes a bleach bath for use in a .dye bleach-out process containing a fixing agent, a strong acid and a mild oxidizing agent capable of oxidizing metallic silver to a silver salt.

Any mineral acid may be usedas a strong acid,

t such as hydrochloric acid, hydrobromic acid, hy-

dye images, such as a solution of cupric chloride.

The treatment of photographic elements by the bleaching-out process therefore generally involves five operations, apart from the necessary washing steps, namely: (1) development; (2) fixing out theundeveloped silver halide; (,3) dye-bleaching; (4) oxidation of the residual silver to a silver salt; (5) fixing out the silver salt.

It has now been foimd possible to employ a bleach bath which will simultaneously accomplish operationsi2), (3) {(4) "and (5),renderingunnecessary any separate operation for fixing out residual silver halide and for removing unused silver. By reduction in the number-of chemical operations it is also possible to reduce the num-' ber of washes andthis accomplishes a great saving in time.

According to the present invention, therefore, in a photographic dye bleach-out process there is fixed out, the dye is bleached, the silver is oxidized and the oxidation product of the silver is fixed out in one operation, provided that a suitable quantity of the mild oxidizing agent is employed. The presence of the mild oxidizing agent also makes itpossible to efi'ect -control oi the gamma of the dye image since therelative con droiodic acid, nitric acid, and phosphoric acid. Among oxidizing agents which can be used may be mentioned ferric chloride, ammonium vanadate, vanadyl chloride, potassium ferricyanide, potassium nitrate and organic compounds such as soluble nitro and nitroso compounds and azo dyes which can rapidly difluse into and'out of an emulsion. I

Examples willnow be given of suitable bleaching baths for carrying out the present inventions:

In this solution, the thiocyanate ion is responsible for the fixing and for the formation of a soluble complex of silver when the silver becomes oxidized. The'complex'formed from the thiocyanate andferric ions acts as th mild oxidizing agent to oxidize the silver not oxidized by the bleaching of the image-forming dye. Th oxyaminophenazine and the dimethyl' quinoxaline act as a bleaching catalyst.

r I Erample 2 v 2 Potassium thiooyanate "grams" 14.0 H1804 (cone) &cubic centimeters; 1.0

2-hydroxy-3-amiriophenazinegrams 0.004 2:3-dimethylquinoxaline do. 0.02 v d0 v 0'1 I 11:0, to cubic-centimeters Example 3 Potassium thiocyanatens gr ams 14.0 H2804 (conc.) cubic centimeters; 1.0 2-hydroxy-3-aminophenazinegrams 0.004

2:3-dimethylquinoxaline do 0.02

Du-Pont Qrange G, Schultz No. 39

H2O, to cubiocentimeters Example 4 Example 13 Potassium thiocyanate grams- 15.0 Thiocarbamide ..grams- A Hydrochloric acid (conc.) Hydrochloric acid (conc.) ....do 4.0

' cubic centimeters 5.0 2:3-dimethylquinoxaline do 0.03 2-hydroxy-3-aminophenazinegrams 0.004 Ferric ammonium sulphate ..do 0.1 2:3-dimethylquinoxaline do 0.03 H2O, to -..cubic centimeters 100 Ferric chloride do 0.05 H3O, to cubic centimeters 100 Example- Thiocarbamide grams..- 5.0 Example 5 Sulphuric acid (conc.) Potassium thiocyanate grams 10.0 cu i entim e Phosphoric acid (cone) 2:8-dimethylqu1noxaiine grams 0.04

cubic centlmeters 1,0 Ammonium vanadate--. ..d0-- 0.025 2-hydroxy-3-aminophenazineL grams 0.004 H20. cu cent Ferric ammonium sulphate do- 0.1 I Example 15 2:3-dimethylquinoxaline ..d0 0.02 Potassium aluminum sulphate do 3.0 Potassium tmocyanate"? 1M 20, to cu'bic centimeters 10o Hydrochloric acid (1301100 cubic centimeters--. 4.0 Example 5 -2:a-dimethylquinoxaline grams 0.03 I Potassium thiocyanatee grams 12.0 os et y 'a i Hydrochloric acid (cone) H20. to --cubic centimeters" 100 (millimeters-w In Examples 13 or 14, the thiourea serves the 2:3 -dimethylquinoxaline "grams" 4.04 same purpose as potassium m Ferric ammonium The bleaching baths of the foregoing examples to centimeters-10o may be used, for example, for the production Example 7 of dye images in a three-layer him, the emulsion Potassium thiocyanate grams 10.0 izg g gggg respectively contaml me l l fiydmhloric acid mom") A yellow dye which was prepared fromtetrazotized tolidinedisulphonic acid coupled with 2- Potassium ferricyanide do 0.1 h1 o-5 hydr0xyto1uene. to centimeters" A magenta dye which was prepared from Example .3 zegrgzotimed t2 h:5:2':5'-teet;amfii;1hyi-4i:gidnop eny me ane coup ace y g gf im g fi i j a A cyan dye, Pontamine Fast Green 58L, manudim 0 factured by E. I. du Pont de Nemours and Comethylquinoxaline do 0.03 pany io-Nitman-mne In the foregoing examp s the concentrations T "cubic centimeters" 40 of each component may varied within wide Example liniits witmkilut gsglougly afiectiagn the bleacdr:

aconof e ,utpermi gthera Pot ssi m thiocyanate --,-8 bleaching and contrast 01 the dye ima es to he Hydrochloric acid (cone) -do 4.0 4 adjusted as desired msmmethylqumoxalme 093 5 The invention is not limited to th above Ammnogium vtainadate (or an equivamples which illustrate the use of numerous g ty of vanadyl ch10 oxidizing agents for oxidizing the excess of metale) 032 116 silver, e. g., the ferric, vanadyl, fern-cyanide 'T' b centimeters" or nitrate ions or an az dye or 9, nitro or nitroso Example 10 compound. Our invention comprises all modifications included within the scope of the appended Potassium thiocymte "grams. 12.0 c1aims Hydrochloric acid (conc.) We claim:. cubic centimeter! 51! 1. A method of producing a colored photo- 2:3'dimethy1qum1$a1ine "E 3. graphic image in a gelatino-silver halide layer m containing a dye capable of being decolorized by phone reduction, which comprises exposing and devel-- to Feubic cmctlmetel'su oping the layer to produce a metallic silver image therein, and then'simultaneously bleaching Exam, ,8 11 the dye and fixing out the silver and silver halide KC'NB "grams" L20 in a bath containing an acid bleaching agent. Hydrochloric acid (conc. a a mild oxidizing agent for silver, and a fixing cubic centimeters" 4.0 agent, I 2:3-dlmethylquinoxaline -grains 0.03 2. A method of producing a colored photooor m-nitrobenzene sulphonic acid ..do 0.1 graphic imag in a gelatino-silver halide layer HaQto cubic.centimeters-- 100 containing an azo dye capable of being declor- Example 12 ized by reduction. which comprises exposing and I developing the layer to produce a metallic silver P ta m tmocymte grgmg 101 image therein, and then simultaneously bleach- Hydrochloric acid cubic centimeters..- 5.0 ing the dye a fixing ut the'si ve and si v r 2z3-dimethylquinoumli e; gramg i103 halide in a bath cohtaininglan acid bleaching i-nitroanthraquinone-a-sulphonic v n ferric ions as an oxidizing agent for silver,

acid.- -.-.do-.'-.. 0.05 and a fixing agent.

to --cubic centimeters" 3. A method of producing a colored photographic image in a gelatino-silver halide layer containing an azo dye capable of being declorized by reduction, which comprises exposing and developing the layer to produce a metallic silver image therein, and then simultaneously bleaching the dye and fixing out the silver and silver halide in a bath containing an acid bleaching agent, an azo dye as an oxidizing agent for silver, and a fixing agent.

4. A method of producing a colored photographic image in a gelatino-silver halide layer containing an azo dye capable of being decolorized by reduction, which comprises exposing and developing the layer to produce a metallic silver imag therein, and then simultaneously bleaching the dye and fixing out the silver and silver halide in a bath containing hydrochloric acid as a bleaching agent, a mild oxidizing agent for silver, and a fixing agent.

5. A method of producing a colored photographic image in a gelatino-silver halide layer containingan azo dye capable of being decolorized by reduction,-which comprises exposing and developing the layer to produce a metallic silver image therein, and then simultaneously bleaching the dye and fixing out the silver and silver halide in a bath containing an acid bleaching agent, ferric ions as an ozidizing'agent for silver, and potassium thlocyanat as a fixing agent.

6. A method of producing a colored photographic image in a gelatino-silver halide layer containing an azo dye capable of being decolorized by reduction, which comprises exposing anddeveloping the layer to produce a metallic silver image therein, and then simultaneously bleaching the dye and fixing out the silver and silver halide in a bath containing an acid bleaching agent, an azo dye as an oxidizing agent for silver, and potassium thiocyanate as a fixing agent.

7. A method of producing a colored photographic image in a gelatino-silver halide layer containing an azo dye capable of being decolorized by reduction, which comprises exposing and developing the layer to produce a metallic silver image therein, and then simultaneously bleaching th dye and fixing out the silver and silver halide in a bath containing hydrochloric acid as a bleaching agent, a mild oxidizing agent for silver, and potassium thiocyanate as a fixing agent.

8. A bleach and fixing bath for use in a bleachout process of color photography, containing a fixing agent, a strong acid, and an azo dye as a mild oxidizing agent capable of oxidizing metallic silver to silver ion.

RICHARD V. YOUNG. MERRILL W. SEYMOUR.

CERTIFICATE OF CORRECTION. Patent vm. 2522,081 June 15, 1915.

RICHARD v: YOUNG, E'" AL.

It is hereby certified that error appears in the printed specification of the above nuinbered patent requiring correction as follows: P a-5e 2 first column, line 21;, for "14.01;." read 0,01 and that the said Letters Patentshould be read with this correction therein that the Same may conform to the record of the case in the Patent Office.

Signed and sealed this 51st day of g A. 9 1-5- Henry Van Arsdale, Acting Commissioner of Patents. 

